Exercise and Hypertension

Total energy burn matters more than intensity if you've got high blood pressure.

It's simple in theory: high blood pressure raises your risk of stroke and heart disease, whereas exercise lowers these risks, so people with hypertension should exercise. In practice, there hasn't been much practical research on how much exercise is optimal, and at what intensity, for people who already have high blood pressure. Enter Paul Williams and his long-running National Runners' and Walkers' Health Studies, which include more than 10,000 people who have been diagnosed with hypertension and are using medication to control it. Williams did a sub-analysis on this group, and just published the results in the journal Hypertension.

To no one's surprise, exercise is good for you even (or perhaps especially) if you have high blood pressure. Here's the key graph:

The amount of exercise is expressed in MET-hours per day, where 1 MET (metabolic equivalent of task) is equivalent to your basal metabolic rate (more on this later). The reference group on the far left (less than 1.07 MET-hr/day) are getting less exercise than recommended; the second group (1.07-1.8) are basically meeting the recommendations for physical activity (e.g. 150 minutes of moderate activity per week), but their hazard ratio isn't significantly different from the sedentary group. It's only once you get above 1.8 MET-hr/day that you start to see a significant reduction.

One of the interesting findings was that, in this case, there was no difference between running and walking for people who burned an equivalent amount of energy. This is quite different from some of Williams' earlier findings; for example, running seemed to produce greater weight loss than walking even when the amount of energy burned was the same. As far reducing the risks associated with hypertension, though, intensity doesn't seem to play a significant role – though from a practical perspective, Williams does point out that "one must go ~50% further and take about twice as long to expend the same amount of energy by walking briskly as by running a 12-minute mile."

To plug some numbers in, you can check out MET values from the Compendium of Physical Activities for walking and running. Walking a "moderate pace" of 2.8 to 3.2 mph takes 3.5 METs; running at 10:00/mile takes 9.8 METs (these are average values, needless to say). Overall, Williams found that exercising for 2.7 MET-hr/day, which is equivalent to running 18.5 km (11.5 miles) per week, reduced the risk of death by stroke by 55%, heart failure by 51% , and all-cause mortality by 29% among people with hypertension.

***

Read the Sweat Science book, and follow the latest posts via Twitter, Facebook, or RSS. Also, I'll be speaking about the science of recovery as part of the Evolution of the Athlete webinar series (along with Tim Noakes, Dave Martin, and many others) in October; details here.